In one aspect, this invention relates to a process for converting 1,2-dichlorobenzene (ortho-dichlorobenzene) to 1,4-dichlorobenzene (para-dichlorobenzene). In another aspect, this invention relates to a process for chlorinating benzene and/or chlorobenzene so as to produce 1,4-dichlorobenzene at good selectivity. In a further aspect, this invention relates to modified Friedel-Crafts catalysts for preparing 1,4-dichlorobenzene.
It is known to produce 1,4-dichlorobenzene, generally in conjunction with 1,3-dichlorobenzene, by isomerization of 1,2-dichlorobenzene in the presence of a Friedel-Crafts catalyst such as AlCl.sub.3. It is also known to produce 1,4-dichlorobenzene by chlorination of benzene or chlorobenzene in the presence of Friedel-Crafts catalysts such as chlorides of Al, Sb and Fe. However, there is an ever present need to develop new processes for producing 1,4-dichlorobenzene at higher selectivity by employing more effective catalysts than those presently known. 1,4-dichlorobenzene is used as a monomer for preparing poly(phenylene sulfide).